1. Field of the Invention
The present invention relates to a thermal transfer printer in which heat-fusible or -sublimable ink applied to a ribbon is transferred to a paper sheet by means of Joule heat produced by heating a thermal printing head, and more particularly, to a thermal transfer printer adapted for printing characters and bar codes on paper sheets, such as labels.
2. Description of the Related Art
As an example of the conventional thermal transfer printer of this type, there is a label printer which is disclosed in Japanese Patent Disclosure No. 61-266271 (corresponding to U.S. Pat. No. 4,744,680, issured on May 17, 1988) assigned to the same assignee as the present application.
In this label printer, characters and bar codes are printed on a label sheet by means of a line thermal printing head with a large printing width. In printing, the printing head is pressed against an platen with a ink ribbon and the label sheet between the head and the platen. This prior printer invention is characterized in that a printer unit, in which a line thermal head and ink ribbon supply and take-up spindles are mounted on a pair of frames, is rockably or movably attached to a fixed mechanism section of a casing of the printer.
According to the prior art printer described above, when the thermal printing head is pressed against the platen, the ink ribbon between ink ribbon supply and take-up rolls may slacken, thus failing to produce a clear print and, therefore, entailing defective printing.